1. Field of the Invention
The present invention relates to a transmission and reception device for a fiber-optical sensor system functioning with two wavelengths and to a fiber-optical brancher useful with such a system.
2. Description of the Prior Art
A fiber-optical sensor system with a transmission and reception device of the this type is known from the EP No. 00 54 292. In that this transmission and reception device, a transmitter in the form of a light source emits light with a first wavelength and, at the same time, light with a second wavelength. The emitted light is supplied to the transmitter-side end of the fiber path of the sensor system in essentially free beam propagation by means of two-semi-reflecting mirrors. The light with the first wavelength emerging from the transmitter side end and the light with the second wavelength likewise emerging from the transmitter side end are supplied to the allocated evaluation means, being likewise supplied in essentially free beam propagation over the beam-splitting mirrors and, if need be, over narrow band filters.
The two beam splitter mirrors mean a relatively high loss which, given the manner of functioning of the known sensor system, amounts to 9 dB for the light with the second wavelengh employed as measuring light and amounts to 12 dB for the light with the first wavelength employed as reference light.
Because of the essentially free beam propagation, lenses for beam-shaping and effective in-coupling of light into the fiber path are required, given the known transmission and reception devices so that the optical part of the transmission and reception devices having these lenses and the various mirror and filter laminae is complicated in terms of structure and requires considerable manufacturing outlay.